The APA5 monoclonal antibody reacts with the mouse CD140a molecule, the α chain of the platelet derived growth factor receptor (PDGF receptor). PDGFRa is a receptor tyrosine kinase that forms dimers on the surface upon ligand binding and phosphorylates substrates. Dimers of PDGFR consist of either homodimers of α/α, β/β, or heterodimers of α/β and serve as a substrate for its kinase activity. CD140a is expressed by embryonic tissues and mesenchymal-derived cells of the adult mouse tissues.